The relationship of insulin antagonism or deficiency to plasma glucagon dynamics in diabetes mellitus, obesity, pregnancy, oral contraceptive administration and primary hyperparathyroidism is sought. An in vitro animal model consisting of isolated pancreatic islets perifused in chambers under a number of conditions will define insulin and glucagon secretory dynamics that help to elucidate mechanisms whereby plasma insulin and glucagon disturbances occur in the clinical conditions outlined above. BIBLIOGRAPHIC REFERENCES: Kalkhoff, R.K.: Metabolic effects of progestins. V International Congress of Endocrinology. International Congress Series, Excerpta Medica, New York, 1977 (in press). Shetty, K. R., and Kalkhoff, R. K.: Human chorionic gonadotropin (HCG) treatment of obesity. Arch. Int. Med., 1977 (In press).